If it helps, here is my code for drawing rectangles on multiple sized video streams
#include "stdafx.h"
#include "opencv2/imgproc/imgproc.hpp"
#include "opencv2/highgui/highgui.hpp"
#include <stdlib.h>
#include <stdio.h>
#include <iostream>
#define SSTR( x ) dynamic_cast< std::ostringstream & >(( std::ostringstream() << std::dec << x ) ).str()
using namespace std;
using namespace cv;
Rect box; //global structures needed for drawing
bool drawing_box = false;
struct mousecallbackstruct{
Mat* src;
Mat* overlay;
string windowname;
};
Mat srcoverlay,smallsrcoverlay; //an overlay must be created for each window you want to draw on
void onMouse(int event, int x, int y, int flags, void* param) //it seems the only way to use this is by keeping different globals for different windows - meaning you have to set up all thise ahead of time, and keep track of it and not mix/match windows/frames!! horrible design here.
{
cout << event;
mousecallbackstruct mousestruct;
mousestruct = *((mousecallbackstruct*)param);
Mat* srcp = mousestruct.src;
Mat* overlayp = mousestruct.overlay; // yeah, yeah, i use 7 lines where I could use 3, so sue me
Mat src = *srcp;
Mat overlay = *overlayp;
if(!src.data){
cout << "your void * cast didn't work :(\n";
return;
}
switch( event ){
case CV_EVENT_MOUSEMOVE:
if( drawing_box ){
box.width = x-box.x;
box.height = y-box.y;
}
break;
case CV_EVENT_LBUTTONDOWN: //start drawing
drawing_box = true;
box = cvRect( x, y, 0, 0 );
break;
case CV_EVENT_LBUTTONDBLCLK: //double click to clear
drawing_box = false;
overlay.setTo(cv::Scalar::all(0)); //clear it
break;
case CV_EVENT_LBUTTONUP: //draw what we created with Lbuttondown
drawing_box = false;
if( box.width < 0 ){
box.x += box.width;
box.width *= -1;
}
if( box.height < 0 ){
box.y += box.height;
box.height *= -1;
}
rectangle( overlay, Point(box.x, box.y), Point(box.x+box.width,box.y+box.height),CV_RGB(100,200,100),4); //draw rectangle. You can change this to line or circle or whatever. Maybe with the Right mouse button.
break;
}
}
void iimshow(mousecallbackstruct* mystructp){ //this is where we add the text/drawing created in the mouse handler to the actual image (since mouse handler events do not coincide with the drawing events)
mousecallbackstruct mystruct = *mystructp; //custom struct made for the mouse callback - very handy for other functions too
Mat overlay, src;
Mat* srcp = mystruct.src;
Mat* overlayp = mystruct.overlay;
src = *srcp; // yeah, yeah, i use 9 lines where I could use 3, so sue me
overlay = *overlayp;
string name = mystruct.windowname;
Mat added,imageROI;
try{
//cout << "tch:" << overlay.rows << "," << src.rows << ";" << overlay.cols << "," << src.cols << ";" << src.channels() << "," << overlay.channels() <<"," << src.type() << "," << overlay.type() << "\n";
if(overlay.data && overlay.rows == src.rows && overlay.cols == src.cols && overlay.channels() == src.channels()){ //basic error checking
add(src,overlay,added);
}else{
//try to resize it
imageROI= overlay(Rect(0,0,src.cols,src.rows));
add(src,imageROI,added);
}
imshow(name,added);// the actual draw moment
}catch(...){ //if resize didn't work then this should catch it and you can see what didn't match up
cout << "Error. Mismatch:" << overlay.rows << "," << src.rows << ";" << overlay.cols << "," << src.cols << ";" << src.channels() << "," << overlay.channels() <<"," << src.type() << "," << overlay.type() << "\n";
imshow(name + "overlay",overlay);
imshow(name+"source",src);
}
}
int _tmain(int argc, _TCHAR* argv[]){
VideoCapture cap(0); // open the default camera
if(!cap.isOpened()) { // check if we succeeded
cout << "NO camera found \n";
return -1;
}
Mat src,smallsrc,overlay;
cap >> src; //grab 1 frame to build our preliminary Mats and overlays
srcoverlay.create(src.rows,src.cols,src.type()); //create overlays
smallsrcoverlay.create(src.rows,src.cols,src.type());
srcoverlay.setTo(cv::Scalar::all(0)); //clear it
smallsrcoverlay.setTo(cv::Scalar::all(0)); //clear it
namedWindow( "smallsrc", CV_WINDOW_AUTOSIZE );
namedWindow( "source", CV_WINDOW_AUTOSIZE ); //these must be created early for the setmousecallback, AND you have to know what Mats will be using them and not switch them around :(
moveWindow("smallsrc",1000,100); //create a small original capture off to the side of screen
////////////// for each window/mat that uses a mouse handler, you must create one of these structures for it and pass it into the mouse handler, and add a global mat for overlays (at top of code)
mousecallbackstruct srcmousestruct,smallsrcmousestruct; //these get passed into the mouse callback function. Hopefully they update their contents automatically for the callback? :(
srcmousestruct.overlay = &srcoverlay; //fill our custom struct
srcmousestruct.src = &src;
srcmousestruct.windowname = "source";
smallsrcmousestruct.overlay = &smallsrcoverlay; //the small window
smallsrcmousestruct.src = &smallsrc;
smallsrcmousestruct.windowname = "smallsrc";
setMouseCallback(smallsrcmousestruct.windowname, onMouse, (void*)&smallsrcmousestruct); //the actual 'set mouse callback' call
setMouseCallback(srcmousestruct.windowname, onMouse, (void*)&srcmousestruct);
for(;;){ //main loop
/// Load an image
cap >> src;
if( !src.data )
{ return -1; }
resize(src,smallsrc,Size(),.5,.5); //smaller scale window of original
overlay = *srcmousestruct.overlay;
src = *srcmousestruct.src;
iimshow(&srcmousestruct); //my imshow replacement. uses structs
iimshow(&smallsrcmousestruct);
if(waitKey(30) == 27) cin.get(); //esc pauses
}
cin.get();
return 0;
}
